Characteristics of an object can be expressed by a spectrum thereof, which includes a scattering spectrum from the environment and a radiation spectrum from its own body. Different objects and materials can be recognized by the spectra which can improve the ability of remote sensing when combined with 2D images thereof.
Devices collecting both images and spectra are usually multispectral and hyperspectral scanners. For example, airborne and satellite-borne multispectral and hyperspectral scanners developed abroad which are installed on air vehicles can cover a comparative wide range of ground by scanning mirrors rotating to have instantaneous visual fields move in directions perpendicular to flying directions. However, for original data obtained by the devices need to be transmitted back to the ground for processing and a processing rate thereof is slow, the devices are only applicable for unreal-time detection of static scenes instead of moving subjects and dynamic behaviors.